ultrasonic cleaner not working

NF-

Are you familiar with crystal oscillators? That is roughly how the ultrasonic transducer is connected, but as a high power oscillator. The remainder of any electronics would be for a timer/controller.

The transducer probably has a ceramic element, and is constructed somewhat like a capacitor. It should have electrodes fired and/or plated onto opposing surfaces, one of which may be glued to the bottom of the tank. One failure mode would be a fractured ceramic. You might check it as a capacitor to see if it is shorted or leaky.

I don't know how practical this would be, but one test might be to connect the transducer to a sensitive oscilloscope and see if mechanical vibrations result in electrical waveforms.

Be sure you always have a liquid in the tank when testing. Unloaded, the transducer is more likely to fracture.

When you get it working, you should wear hearing protection while it operates.

Fred

Also use fluid! I would use a lamp connected in series with line in after replacing components. I worked on a fairly complex model a while back and gave up because I didn't have enough documentation. The circuit will usually either work or not, but in my case just refused to generated enough power. The frequency and resonators must be right on value. The transducer must match the opperating frequency of the oscillations.

greg

Thanks for the insight, Greg. I'll try to set something up for testing.

Fred, thanks. Your suggestions will be followed.

I just didn't want to replace the fuse and blown diodes and power the thing up not knowing what to expect. Just before the fuse an diodes went out, it was making its "normal," low frequency/volume buzzing sounds. Naturaly, I could not hear the high frquency stuff but parts were getting somewhat cleaned.

Cheers, Norman

I used to repair ultrasonic cleaners back in the 70's. The most common problem was the transducers becoming partially unglued from the tank. I always assumed stuff had been dropped into the tanks, but perhaps the ultrasonic energy caused it. I used to pry the transducers off the tanks and then glue them back on with a silver-loaded epoxy. This usually worked and was quicker and cheaper than a new tank assembly. I would usually test the generators by substitution with a good unit, something you can't do. If they needed repair I would run them with a resistive dummy load, but I can't remember what value it was.

In message , Nortonfan writes

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Neil J. Harris

Neil,

Silver-loaded epoxy? Was this part of the composition of the epoxy type, or was it something added into the mix during application?

Thanks, Norman

Norman-

I don't know, but would expect it to have been part of the composition. I believe the silver is needed to provide electrical connectivity to the transducer, but it might also serve the purpose of making a more rigid attachment between the transducer and the tank.

I wonder if any service information is available from Bulova?

Fred

Fred,

I searched for silver charged epoxies and did find several types. I've also searched the web and found no contact information for Bulova ultrasonic cleaners. There is an address, however, for the watch line. Before I began taking a screwdriver to it, I wanted to have a firm understanding of its operation and a realiable source for parts. Thanks to fellows like you, this job is not as daunting as I once envisioned. However, I still have no sources for parts nor significant technical information on this particular unit. A similar unit to the one I have is presently on Ebay for well over $200 and will probably exceed that, considerably, during the feeding frenzy of the last minutes of auction.

I've replaced the blown diodes and the protection fuse and powered the unit. It makes a rather annoying buzzing sound, not as loud as an old doorbell buzzer - but, annoying, nonetheless. My concern is that if the epoxy joint has cracked (though I have not seen any cracks), this would lead to failure of the transducer. I would prefer to prevent this possibility and, at the same time, I'm a bit gun-shy of tampering with it for fear of making things worse. The old wisdom of "if it works, don't fix it." Maybe, it's supposed to make the buzzing sound?

Thanks, Norman

That buzzing sound may be normal. These things are far from silent and the ultrasonic waves are often not CW. Have you tried anything in the tank? I assume you had water in the tank at least.

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Norman-

If the power rectifier diodes were blown, I would suspect that any filter capacitors associated with the output of the diodes might have also been damaged. Obviously they aren't shorted, or you would have blown more diodes!

As you have noted, Bulova is a watch company. They may have had some other company make the ultrasonic cleaner for them. A little research might turn up two or three companies that have produced them, and there may be a model that looks identical to yours.

Back in the 70s I built the Heathkit GD-1150 Ultrasonic Cleaner. The operational test was to use a 1" strip of aluminum foil held vertically in

1" of water, and expect a minimum of ten pinholes created in the foil after 30 seconds of operation.

Fred

The silver was in the epoxy, it made the epoxy electrically conductive. The transducers were like a big ceramic capacitors with metalising on both sides. I seem to remember that when the transducers became detached some of this metalising came away from the transducer. Using the silver loaded epoxy to re-attach the transducer fixed this as well. I remember talking to a bloke at Araldite about it. They made a specific product for this application but it was not readily available in small quantities, so we used a similar product from RS Components. (Also made by Araldite.) I've had a look at the RS website but I can't see the product I used, it was 30 years ago! they do list a silver loaded product but it seems to be American. Araldite have long since shut up shop in Birmingham (UK). It may well be an abandoned technology by now. The electronics industry was a big user or ultrasonic cleaners, but its all "no-clean" stuff now (and all gone to China!)

In message , nortonfan writes

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Neil J. Harris

Hi guys!

To all of you who replied to my questions, thanks! My ultrasonic cleaner is working within its capabilities and I'm very pleased that I did not blow anything up, including myself! Most of it, thanks to you guys. I learned something about how ultrasonic cleaners operate, cleaning solutions and, most of all, the valuable resource and support this forum provides.

Cheers, Norman C